Like all the major rift valley lakes of the eastern arm of the Rift Valley, lake Manyara is the remnant of a much larger lake, which goes
back in time to more or less 1.3 Ma.
The eastern extension of the lakes stretches as far as the village of Makuyuni, where many terrace deposits can be distinguished.They have been
studied by several scientists in the past, and Makuyni is the ideal place to have a look at them. Several scientists of Ecoscience have been checking them out.
A mostly nephelinitic bedrock (probably deposits of the close by Essimingor volcano) is visible on which the lake deposits sit. One can distinguish lower beds (lacustrine deposits) and higher beds (river deposits).
The lake has been retreating over this period and what is left of it will probably disappear in the near future. Under the actual lake -the western side of the ancient lake-, geophysical studies have revealed sedimentary deposits of a round 3 km thickness, showing how this part of the Rift Valley has been subsiding over the years.